Congener-specific action of PBDEs on steroid secretion, CYP17, 17β-HSD and CYP19 activity and protein expression in porcine ovarian follicles.

Abstract The available data on reproductive toxicity of PBDEs are limited. In the present study we evaluated the direct effects of BDE-47, -99 and -100 on porcine ovarian follicular steroid secretions and the activity and expression of enzymes involved in its synthesis. Follicles were exposed to BDE-47 (0.5, 25 and 50 ng/ml), BDE-99 (0.25, 10 and 17.5 ng/ml), or BDE-100 (0.1, 4 and 12.5 ng/ml) for 24 h. Progesterone (P4), androstenedione (A4), testosterone (T) and estradiol (E2) levels in the media were determined by EIA. CYP17, 17β-hydroxysteroid dehydrogenase (17β-HSD) and CYP19 activity was measured by conversion of P4 > A4, A4 > T and T to E2, respectively. Protein expression of CYP17, 17β-HSD and CYP19 was measured by western blot. All of the congeners explored in this study increase testosterone secretion. However, in the case of BDE-47 due to activation of 17 β-HSD and BDE-100 due to activation of CYP17, a corresponding failure to activate CYP19 expression and inhibition of CYP19 activity was seen. The lack of an effect of BDE-99 on the expression and activity of all of the investigated enzymes indicates action on enzymes before progesterone secretion, i.e., STAR or 3β-HSD activity.